During normal operation of an internal combustion engine, a small portion of the air fuel mixture fed to the engine cylinders passes by the pistons and the piston rings into the crankcase before combustion occurs. Also, after combustion of the air fuel mixture in the combustion cylinders, combustion exhaust gases are forced past the piston rings into the crankcase. The unburned air fuel vapor mixture and combustion exhaust gases include water vapor, oil vapor, carbon dioxide, carbon monoxide, and soot combustion materials and are collectively called "blow-by" gases. The blow-by gases occur due to a breakdown in the integrity of the combustion chamber, primarily caused by damage or prolonged wear to the piston rings during operation cycles. However, blow-by gases can also occur from damage to the pistons, the combustion cylinder walls, or the valve guides and valve stems, which, for simplification, shall collectively be referred to as the combustion chamber.
The releasing of such vapors and gases from the crankcase into the ambient atmosphere is a direct cause of the oil residue that collects along roadways. To reduce the emission of blow-by gases to the atmosphere, many types of engines employ a positive crankcase ventilation (PCV) system, wherein engine blow-by gases are recycled back into the air fuel induction system of the engine. However, in certain engines, particularly in diesel engines and internal combustion engines employing fuel injection, a PCV system is not entirely advantageous in terms of fuel efficiency and hydrocarbon exhaust reduction. In fact, many diesel engines vent their blow-by gases directly into the ambient atmosphere, thereby creating the oil residue seen on roadways.
An efficient method for reducing the formation of these blow-by gases is periodic inspection of the pistons and the piston rings for excessive wear or possible damage. However, inspection of these parts is an expensive process. Since the extent of blow-by gas formation in the crankcase is directly related to the integrity of the combustion chamber, a method and apparatus for measuring the extent of blow-by gas formation in the crankcase would provide a much less expensive means for gauging the performance of the combustion chamber, in general, and the piston rings, in particular, in preventing the formation of blow-by gases.
In addition, while PCV systems help minimize contamination of the oil lubrication system and can increase the fuel efficiency of internal combustion engines, they can create the potential for damage to the engine. In the event of a substantial leak within the combustion chamber caused by, for example, a blown piston ring, a burned piston, or a dropped valve, a substantial amount of the oil can be blown out of the crankcase. With a PCV system, this oil is routed to the air intake manifold and, eventually, burned along with the air-fuel mixture, depriving the lubrication system of needed oil, which could result in serious damage to the engine.
Accordingly, there is a heretofore unaddressed need in the industry for a method and apparatus for gauging the condition of the combustion chamber as well as preventing complete oil blow out upon damage to the pistons or the piston rings.